If the interrupt signal is likely to be too short to be able to poll in the
ISR, then maybe you could use something like an SR flip flop for each IRQ.
The incomming interrupt would set the output of the flip flop which can be
diode OR'ed to the int pin.  The ISR would have the responsibility of
clearing each flip flop after servicing its interrupt.  With a bit of
cunning (and a resistor or two) you could use the same PIC pin to read and
reset the flip flop.

Mike

> -----Original Message-----
> From: KŸbek Tony [SMTP:tony.kubek@FLINTAB.COM]
> Sent: Tuesday, May 30, 2000 10:51 AM
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      [PIC]: Multiple IRQ'S ?
> 
> Hi,
> What's the 'best' way to interface several external irq requests ?
> PortB change feature seems 'no-go', OR'ing several irq's
> to the INT pin seems doable ( and then poll which one it was )
> but potentially dangerous ( strong possibility of missing one ).
> 
> Any suggestions ?
> 
> /Tony
> 
> 
> Tony KŸbek, Flintab AB            
> ΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣΣ
> E-mail: tony.kubek@flintab.com
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